4 Replies Latest reply on Mar 26, 2008 3:23 AM by Jonas Hummelstrand

    Keying DV Footage, reduce pixelated edges?

    Level 1
      I shot my on-screen host on a green screen using a 3-chip prosumer camera. The source footage is 'good' (not great). I got a decent key out of the footage, but I find that his edges are noticably pixelated, the edges are almost dancing at a pixel-level in my outputs. Any suggestions on how to fix this?

      Using Adobe AFX CS3
        • 1. Re: Keying DV Footage, reduce pixelated edges?
          bogiesan-gyyClL Level 3
          That's how DV is. Why we tolerate DV as an acceptable format is beyond me but we're stuck with it.

          Better keyers (expensive keyers) have proprietary sampling and correction techniques for lossy and blocky formats like DV. DV Matte Garage and Boris keyers are both superb.

          You can improve DV by using different key settings and matte processing on stacked copies of the same footage. It's tedious but kind of fun. You learn a lot in the process.

          • 2. Re: Keying DV Footage, reduce pixelated edges?
            Todd_Kopriva Level 8
            From your brief description, it sounds like your issue may be a result of blockiness from compression artifacts in your footage. DV and similar formats throw away a lot of color information that you need for a smooth key.

            Have a look at the "Keying overview and tips" section of After Effects CS3 Help on the Web. It links to Jonas Hummelstrand's website for some tips and to a handy animation preset (KeyerForDV) that automates some of the tedium of keying DV footage.

            Let us know if that page doesn't help.
            • 3. Re: Keying DV Footage, reduce pixelated edges?
              Mylenium Most Valuable Participant
              As David already pointed out - ultimately the limitations are in the source format itself. There are a few tricks like duplicating the layer, blurring it by 4 pixels and using the Color blendmode to reduce the prominence of some of the artifacts as there are plugins like RevisionFX' SmoothKit that can do this more selectively before applying the actual keyer, but one can only go so far... From what it sounds like, some of your problems could have been minimized by better preparation and on-set lighting (properly lit footga will distribute the artifacts differently and less noticable), so maybe keep that in mind for the future. For your current issues you might consider employing a few "dirty" tricks like using the Auto Color and Auto-Levels effects post-key to reduce some of the flicker or using the Timewarp effect with a setting of 100.1% to force it to interpolate some of the dancing pixels. Depending on the background you will insert, also simply consider its color bleed/ light wrap to disguise some of the edge issues.

              • 4. Re: Keying DV Footage, reduce pixelated edges?
                Jonas Hummelstrand Level 2
                There's also a "Reduce DV Artifacts" Animation preset that ships with After Effects CS3 and 7.0.

                - Jonas Hummelstrand